. Elementary text-book of zoology, general part and special part: protozoa to insecta. Animals. 194 PEOTOZOA. transverse fission, and also by spore formation in an encysted condition; the latter method seems in many forms to be preceded by conju- gation. The best known species are Cercomonas Duj. and Trichomonas Donne, of which the first is characterised by the possession of a caudal filament, while Trichomonas has an undulating low of cilia close to the flagella, which are usually two in number (fig. 133). They live principally in the intestines of Vertebrates, but are also found in Invertebr
. Elementary text-book of zoology, general part and special part: protozoa to insecta. Animals. 194 PEOTOZOA. transverse fission, and also by spore formation in an encysted condition; the latter method seems in many forms to be preceded by conju- gation. The best known species are Cercomonas Duj. and Trichomonas Donne, of which the first is characterised by the possession of a caudal filament, while Trichomonas has an undulating low of cilia close to the flagella, which are usually two in number (fig. 133). They live principally in the intestines of Vertebrates, but are also found in Invertebrates. Cercomonas intestinalis Lumbl. and Trichomonas vaginalis Donne, are found in Man. The Monads,* which cannot be sharply separated from the Monadina!, are simple cells free from chloi-ophyll, the swarm spores of which iTsually pjiss into an amoeboid stage, and after I'eceiving nourish- ment enter u^xin a motionless stage characterised by the possession of a firm cell-membrane. A number of them (Monas, Fseudos])ora, doIpodeUa), the so-called Zoospores, are mastigopods resembling the mastigopods (swarm spores) of !Myxo- s^^ Y^L^ih-' mycetes, and, with the exception of ^^ CoIpodeUa, grow up to ci-eeping Amcebje which protrude pointed pseudopodia. In this stage they may also be simply regarded as small plasmodia, especially Avhen, as in Jlonas amyU, several masti- FiG. , Cerco«u,nas gopods fusc together to form the amoeba. h, Triehomonat vaginalis (after R. They thcu take—in Colpodella M-ithout Leuckart). first entering the amoeba stage—a globu- lar form, their surface develops a membrane, and in this cyst they break up by division of protoplasm into a number of segments which pass out as swarm spores and rej^eat the course of development {Coljyodella jnignax to , Pseudospora volvocis). Other Monads, the so-called l'etrap)lasta [Vamjyijrella, Xuclearia), do not pass through the mastigopod (swarm spore) stage. Their pro- toplasm during the i
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectanimals, bookyear1892
